The Proof-Of-Concept Vehicle (POCV) will be battery powered, and only run the bare essentials needed to navigate the craft on a small body of water, a lake for example. The RPi will be tasked with running the Electronic Speed Controller (ESC) which in turn manages the electric motor, taking GPS positioning information and combining that with waypoint and route information to calculate the rudder commands to navigate the POCV to predetermined locations, and take photographs and or video during its test missions.

The FishPi Wiki (link) has a section devoted to the Proof-Of-Concept Vehicle. It contains information on the Hardware being used in the POCV, details about the Base-Station, and in-depth explanations of the POCV's systems.